In general, batteries are used in mobile devices such as a mobile phone and a personal digital assistant (PDA).
Lithium ion batteries are the most broadly used in mobile devices. However, the lithium ion batteries are heated when overcharge or overcurrent occurs. Furthermore, if they are continuously heated and thus an increase in temperature occurs, a risk of explosion as well as a reduction in performance may be caused.
Accordingly, a typical battery has mounted thereon a protection circuit module for sensing and preventing overcharge, overdischarge, and overcurrent, or is connected to an external protection circuit for sensing overcharge, overdischarge, and heating, and interrupting the operation of a battery.
The above-described conventional protection circuit is generally formed by soldering a protection integrated circuit (IC), two field effect transistors (FETs), a resistor, and a capacitor to a printed circuit board (PCB) substrate. However, the conventional protection circuit is not easily reduced in size because the space taken by the protection IC, the two FETs, the resistor, and the capacitor is excessively large.
Also, an additional process is required to mount the protection circuit on a battery pack. Furthermore, after the protection circuit is mounted, external or internal connection terminals of the protection circuit should be connected via patterns or exposed terminals of the PCB substrate by additionally performing wiring or wire bonding.